1. Field of the Invention
This invention relates to the sealing of chimneys having concentric walls defining a tubular pressurized air space therebetween.
2. Description of the Background Art
In one form of chimney such as used in industrial applications, the chimney includes a tubular inner liner and a tubular outer wall spaced radially concentrically from the liner to define a space therebetween. Pressurized air or similar fluid is provided in the space to prevent ingress of products of combustion from the interior of the liner into this space so as to prevent such products of combustion from adversely acting on the outer wall, which is conventionally formed of concrete.
A number of seals have been developed for sealing the upper end of the space between the liner and outer wall. A serious problem arises in the construction of such seals in that substantial relative movement may occur between the liner and outer wall in the normal use of the chimney. Such chimneys may have a height of up to approximately 700 feet and, thus, substantial movement may occur as a result of wind forces, etc., acting on the chimney over such a great vertical extent. Illustratively, the chimney may have a movement of one and a half to two feet at its upper end in such a construction.
Because of the differential movement of the liner and outer wall, a seal connected therebetween may have substantial strains induced therein, tending to crack or break the seal. One example of such a seal is illustrated in U.S. Pat. No. 4,191,099 of Victor H. Strahl. In that patent, the seal includes a flexible annular boot. Spring-biased support members are supported on the outer wall of the chimney and connected to an annular seal ring to which a flexible edge portion of the boot is connected to be supported in sealing relation with a lower annular surface of a hood mounted to the liner. The flexible boot and biasing means are relatively expensive and servicing and maintenance thereof at the top of such a 700-foot chimney is relatively difficult.